Recent changes to Async are now backward compatible.

lib/concurrent/async.rb

@@ -128,22 +128,23 @@ def self.validate_argc(obj, method, *args)
 
     # @!visibility private
     def self.included(base)
+      base.singleton_class.send(:alias_method, :original_new, :new)
+      base.send(:private_class_method, :original_new)
       base.extend(ClassMethods)
-      base.send(:private_class_method, :new)
-      super(base)
-    end
-
-    # @!visibility private
-    def self.extended(base)
-      base.extend(ClassMethods)
-      base.send(:private_class_method, :new)
       super(base)
     end
 
     # @!visibility private
     module ClassMethods
+
+      # @deprecated
+      def new(*args, &block)
+        warn '[DEPRECATED] use the `create` method instead'
+        create(*args, &block)
+      end
+
       def create(*args, &block)
-        obj = self.send(:new, *args, &block)
+        obj = original_new(*args, &block)
         obj.send(:init_synchronization)
         obj
       end
@@ -269,6 +270,22 @@ def executor=(executor)
         raise ArgumentError.new('executor has already been set')
     end
 
+    # Initialize the internal serializer and other stnchronization mechanisms.
+    #
+    # @note This method *must* be called immediately upon object construction.
+    #   This is the only way thread-safe initialization can be guaranteed.
+    #
+    # @raise [Concurrent::InitializationError] when called more than once
+    #
+    # @!visibility private
+    # @deprecated
+    def init_mutex
+      warn '[DEPRECATED] use the `create` method instead'
+      init_synchronization
+    rescue InitializationError
+      # suppress
+    end
+
     private
 
     # Initialize the internal serializer and other stnchronization mechanisms.

spec/concurrent/async_spec.rb

@@ -8,6 +8,8 @@ module Concurrent
       Class.new do
         include Concurrent::Async
         attr_accessor :accessor
+        def initialize(*args)
+        end
         def echo(msg)
           msg
         end
@@ -34,8 +36,16 @@ def with_block
 
     context 'object creation' do
 
-      it 'makes #new private' do
-        expect{ async_class.new }.to raise_error(NoMethodError)
+      # Will be added in 1.0 once deprecated methods are removed
+      #it 'makes #new private' do
+      #  expect{ async_class.new }.to raise_error(NoMethodError)
+      #end
+
+      # Will be removed in 1.0 once deprecated methods are removed
+      it '#new delegates to #create' do
+        args = [:foo, 'bar', 42]
+        expect(async_class).to receive(:create).once.with(*args)
+        async_class.new(*args)
       end
 
       it 'uses #create to instanciate new objects' do
@@ -45,7 +55,7 @@ def with_block
 
       specify '#create initializes synchronization' do
         mock = async_class.create
-        allow(async_class).to receive(:new).and_return(mock)
+        allow(async_class).to receive(:original_new).and_return(mock)
         expect(mock).to receive(:init_synchronization).once.with(no_args)
         async_class.create
       end